If I have 10 tabs opened, I have to close each one using \":q\" separately.
How can I close them all at once?
You can use any of these Vim Ex commands to Exit Multiple Windows And Buffers:
:qa :qall
Exit Vim, unless there are some buffers which have been changed. (Use :bmod to go to the next modified buffer). When 'autowriteall' is set all changed buffers will be written, like :wqall.
:conf qa :confirm qall
Exit Vim. Bring up a prompt when some buffers have been
changed. See :confirm.
:qa! :qall!
Exit Vim. Any changes to buffers are lost. Also see :cquit, it does the same but exits with a non-zero value.
:quita :quitall :quita! :quitall!
Same as :qall.
:wqa :wqall :xa :xall
Write all changed buffers and exit Vim. If there are buffers without a file name, which are readonly or which cannot be written for another reason, Vim will not quit.
:conf wqa :confirm wqall :conf xa :confirm xall
Write all changed buffers and exit Vim. Bring up a prompt
when some buffers are readonly or cannot be written for
another reason. See :confirm.
:wqa! :xa! :wqall! :xall!
Write all changed buffers, even the ones that are readonly, and exit Vim. If there are buffers without a file name or which cannot be written for another reason, Vim will not quit.
To read about these in Vim, type the following Ex command
:help window-exit